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PHM 142 Midterm review Questions With Complete Solutions
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PHM 142 Midterm review Questions With Complete Solutions
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PHM 142 Midterm review Questions With CompleteSolutions
Tips on this midterm. Henderson's questions are very detail-
oriented, but he doesn't like answers to be wordy.
At one point in the course, he may say that using abbreviations
in the test is okay, but some students were docked marks for
using abbreviations. It's best to use the full name of a
protein/structure if possible.
The last few cards in this set are based on the summary slides of
OUR year's presentations. Be sure to flip through your year's
presentations' summary slides and take information from those
instead. The questions on the presentations are generally shorter
(he looks for a single word), so try to ace those.
In general, just try to know everything (I know it sucks). Study
with your classmates, come up with mnemonics, just do
anything to cram all the information in your head.
Apart from the pyrrole rings, what else does the heme iron bind?
Correct Answers The iron atom in heme binds to OXYGEN, as
well as an amino acid in hemoglobin/myoglobin.
Define saturation, in terms of enzymes. Correct Answers #
bound active sites / # potential active sites
Describe acetaminophen-derived liver poisoning. Correct
Answers Acetaminophen is metabolized for excretion via
sulfation or glucuronidation. If these two mechanisms are
saturated, then a toxic quinone intermediate will form.
,This toxic quinone intermediate will target -SH groups in the
liver and cause liver cell necrosis.
This necrosis can be prevented by glutathione conjugation to the
toxic intermediate, or N-acetyl cysteine can be administered,
which would also give another -SH site for the acetaminophen
metabolite to attack.
Describe drug induced hemolytic anemia. Correct Answers A
drug enters the RBC. The drug then undergoes redox reactions:
reduction of the drug results in oxidation of oxyHb (Fe2+) to
metHb (Fe3+). Conversion to metHb releases reactive oxygen
species into the cell.
If the ROS are left unchecked, membrane damage and hemolysis
will occur.
Thus, G6PD deficient patients are more susceptible to this
anemia.
Describe fast twitch muscle fibres. Correct Answers Used for
brief duration.
Energy is primarily from anaerobic glycolysis (so low
mitochondria conc.).
Glycogen content higher.
Myoglobin content is lower (muscles are whiter).
Describe how low iron concentration controls the synthesis of
ferritin. Correct Answers The IRE stemloop is found on the 5'
end (upstream) of the mRNA. When iron is low, the IRP binds
to the IRE and prevents ribosomes from translating the mRNA.
This will decrease the concentration of ferritin.
,Describe how low iron concentration controls the synthesis of
transferritin. Correct Answers The IRE stemloop is found on
the 3' end (downstream) of the mRNA. When iron is low, the
IRP binds to the IRE and stabilizes the mRNA from
degradation.
Importantly, the translational efficiency is not affected, only the
stability of the mRNA.
This will increase the concentration of transferritin.
Describe RBC destruction in hemolytic anemia. Correct
Answers Radical oxygen species are released when oxyHb is
oxidized to metHb. ROS can then attack RBC membrane,
leading to destruction of membrane.
Black urine is one symptom of hemolytic anemia.
Describe slow twitch muscle fibres. Correct Answers Used for
sustained activity.
Energy is primarily from oxidative metabolism (high
mitochondria conc.)
Muscles are highly vascularized (O2 delivery).
Myoglobin content is high (muscles are redder).
Describe the action of cystathione beta-synthase (CBS). Correct
Answers CBS will convert homocysteine to cystathione, and
then another enzyme converts cystathione to cysteine. Vitamin
B6 is an important cofactor for CBS.
This acts as another pathway to reduce homocysteine
concentrations in the body.
Describe the action of glutathione reductase and glutathione
peroxidase. Correct Answers Glutathione reductase uses the
, reductive power of NADPH (-> NADP+) to oxidize GSSG to
GSH.
Glutathione peroxidase then uses the oxidative power of GSH (-
> GSSG) to reduce H2O2 to H2O.
Describe the action of methylene blue on Hb. Correct Answers
Methylene blue will use the reductive power of NADPH (->
NADP+) to change metHb (Fe3+) to oxyHb (Fe2+). Methylene
blue is converted to leucomethylene blue
Since it uses NADPH, methylene blue cannot be used in G6PD
deficient patients.
Describe the effect of B12 deficiency in the 1 carbon pathway.
Correct Answers B12 is a cofactor for methionine synthase.
When B12 is deficient, there will be a buildup of the 5-methyl
THF and homocysteine.
Describe the Fenton reaction. Correct Answers Fe is oxidized
from Fe2+ to Fe3+, which breaks hydrogen peroxide into a
hydroxyl ion and a hydroxyl free radical.
Describe the generation of folate derivatives, starting with THF
and ending with 5-methyl-THF. Correct Answers This pathway
is used to deal with methanol found in the body (either as a
byproduct or through diet).
Methanol enters the body and is oxidized to formate (one carbon
CA).
Formate is attached to THF via an enzyme which uses ATP.
This forms 10-formyl-THF. 10-formyl-THF will isomerize into
5-formyl-THF because they are energetically equivalent.
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